Telephone-exchange system.



F. H. 'McBERTY TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED JULY 27, I910. 1,159,595.

7 SHEETS-SHEET 1.

Patented Nov. 9, 1915; I

F, a. MCBEETY, T. EPHONE EXCHANGE SYSTEM APPLICAUG?! man mu 27,1910.

7 SHEETS-SHEET 2- Patented Nov. 9, 1915.

Mfnesses:

F. R. McBERTY. TELEPHONE EXCHANGE SYSTEM.

Patented Nov. 9, 1915.

q a, APPLICATION FILED JULY 27,1910. LE59 59a,

7 SHEETSSHEET 3 T3 my] mu h Eu haw .6 M ug Luci! L izll. I!!! 11?: IHH MHWII .lilif m m wliz Paten 2* MCBERTY. J'ELEPHOHE EXCHANGE SYSTEM. APPLICATION man JULY 27; 19:0.

ted Nev. 9, 1915. I SHEETS-SHEET lixirliaafiizfi 335; 1 .r I I l 113-25195: ind.

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F. R. McBERTY. TELEPHONE EXCHANGE SYSTEM.

7 S'HEETEHSHEET 5.

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35 MVN TELEPHONE EXCHANGE SYSTEM. APPLICATION FiLED JULY 27, 3910.

TSHEETS-SHEET 6- F. H. McBERTY. TELEPHONE EXCHANGE SYSTEM. APPLICATION FILED JULY 27. 1910. 1 159 1595. Patented Nov. 9, 1915 7 SHEETS-SHEET 7- HIllllllmmhqwmmmum.l

; 7 M ZW a rom FRANK R. MCBER'IY, 0]? NEW? ROCHELLE, NEW YORK, ASSIGNGR- TE; EJE$TEZRN ELECTRIC COMPANY, OF NEW YORK N. Y., A CGRPORAIION OE ELLINGISL TELEPHONE-EXCHANGE SYSTEM' Specification of Letters Patent.

Patented Nov. 9, 191.5.

To aZZ whom it may concern:

Be it known that I, Fur-m1; R MCBERTY, citizen of the United States, residing at New Rochelle, in the county of ll estchester and State of New Yorln have invented a cer tain ne and useful Improvement in Telephone-Exchange Systems, of which the fol lowing is in full, clear, concise, and eXac description.

This invention relates to telephone exchange systems and its objects are in general to provide improved means for the control of various switching and si n-aling devices thereof, whereby the answering of subscribers calls and the interconnection and dis connection of subscribers lines may be etfected with rapidity and. in an orderly and eflicientmannen The invent-ion is a" SPBCBS to various *y change systems in in which it is efiecce cally operated switches sending apparatus at h scribers lines. l'cre nec'ally, however the invention is up to semi-automatic systems wherein the sending apparatus is located at the central otiice and arranged for or in accorca'nce can plug" and aclr switcin While the connections to the lines wanted are made, in part at least, by mechanical selector switches under the control of the sending apparatus The system herein described is one in which the initial connection is made by a plug and jack switch to extend the circuit of a calling line to a cord circuit which terminates in an automatic selector switch, the sending mechanism being temporarily associated with the cord circuit for the purpose of controlling the operation of said selector switch to secure the connection desired.

One feature of the invention has for its ob ect to rovicle an im rove d switchin 's stern which may be controlled with great flexibility to connect an operators telephone set with the connecting circuits of a telephone exchange system. The system depends primari switch mechan eratcrs equip-m i a l m he use of sequence t l with the opt'or each. s being call-y, that ul actby the is, in the or movement e ordinary 211558 1 in the first inst. relay in cents of the plug n ed to come at rest in i normal position, 'ators telephone is notconnecte 5. circuit; next, the listening position, in .vh ch the operators telephone is connected in circuit, the movement to this position from normal occurring upon the insertion of the plug in the spring-jack of a line calling; and finally the oil' listening position, in which the operators telephone is disconnected, the sequence switch being arranged to move to ofl listening position upon the insertion of another plug in a springjack of another calling line.

The sequence switch may if desired'thereafter' be caused to move automatically from oil listening position to normal upon the reout of listening position without the insertlon of another. plug. And contacts may be provided on each listening switch whereby in the listening position the said switch is thus placed temporarily under the control of the listening switches of other connecting' circuits; and other contacts may :be provided on each listening switch'whereby in passing from normal to listening position a circuit is closedto a controlling or motor magnet of any other listening'switch that may be in listening position. Individual keys are preferably provided, one for each connecting circuit, by means of which the operator may cause any listening switch to advance from cit-listening position to listening position again, and in such advance movement the listening switch of any other connectingcircuits will be caused, in the manner already statedfito pass out of listen-- in'g position to the oflglistening position.

Another feature otthe invention relates to means for controlling the operation of the automatic switch mechanism or selectors to cause their return movement after being op-. 5

erated for the interconnection of subscrib- Q ers lines. Means 15 prov ded under the control of the calling line connecting switch whereby under certain conditions the. opening of that switch to disconnect the calling line will automatically cause the" return movement of the selector mechanism. This control, however, is checked by the listening switch when in listening position', the arrangement being such that if the listening "switch is in listening position, the calling line may be disconnected withoutefi'ecting; the return movement of the selector.- A cir-- cuit is also pr'ovidedfor the control of the selector, which circuit includes contacts of the cord relay and the listening switch, whereby it the plug is withdrawn when the listening switch is in oil-listening position, said circuit will become closed and the selector switch with its controlling apparatus will. be caused to return to normal. A selfand be caused immediately to return to norlocking relay is provided for controlling theanal, the operator, in case she has made a mistake in the manipulation of the sendin apparatus, being enabled thereby to start new connection immediately. A further feature of the invention relates to the control (if supervisory signals, whereby these signals "are operated in a particular manner to indicate not only the condition of the connected lines, but also the condition of the switching mechanism. The signals may be ordinary electric lamps controlled in local Cir-cults. Two supervisory signals, one for g each of two connected lines and a third or 1 ringing signal for the called line are provided. The supervisory signal forthe called line is first brought into circuit under the control of a sequenceswitch to indicate that the operation of the selector mechanisms is incomplete, this signalbeing switched out of circuit upon connection being completed with the called line. It is thereafter placed under the control of a relay or other electroresponsive device controlled by current flow in the called line. The supervisory signal for the calling line isfarranged not only to indicate the condition of the callingli'ne 35 when connection is made thereto, but also to indicate the condition of the automatic switch'mechanism when connection with the calling line is broken. The signal remains visible after the plug is withdrawn to disconnect the calling line and until the automatic switch mechanism is restored to normal condition. I

For the purpose of illustrating thcseand other features ofItlie invention there is 96 shown in thedrawings accompanying this application the circuits and apparatus which are directly associated with a single selector and a cord connecting circuit of which the selector forms thetermin'al, and 100 also those. parts of the circuits and apparatus ofa sender mechanism and of other selector switch mechanisms 'which are in some manner involved in the control of'the first This mentioned selector and cord circuit. selector is only one of several whichv in a complete system for a very large exchange would be arranged to be'operated succes? sively i i-the establishment of a connection between telephone lines.

The system herein disclosed embodies a number of inventions other than the. one. claimed. Some of these are made the subject matter of certain other applications for patent by me, as follows: 573,516, filed July 23, 1910, and 528,298,

filed November 16, 1909.

In the drawings, Figure 1 shows the ci rcuits and apparatus which are directly associated with a cord connecting circuit ter-'120 minating in a selector switch mechanism, this being the district switch of a large telephone exchange system; Fig. 2 shows the circuits and apparatus-associated with a listening switch, said switch serving to control the connection of an operators telephone set" to {the connecting circuit of Fig. 1; Fig, 3 shows the circuits and apparatus associated with a sender or controlling mechanism and a cord finder, the sender Serial Nos. 116

brush,

outwardlv serving to control the operation of the selector switch mechanism of Fig. l, and the cord finder to establish temporary connection between said sender and the apparatus of said selector switch mechanism. Fig. shows the circuit of a trunk line leading to a called telephone line to which connection may be made by the selector switch mechanism of Fig. 1. Figs. 1. to l inclusive may be arranged to form a single circuit diagram by placing Fig. 2 above, Fig. 3 below and Fig. l to the right of Fig. 1. Fig. 5 shows in skeleton form a plurality of connecting' circuits of one operators position and a plurality of subscribers lines to make clear the arrangement of listening switch contacts, whereby the connections of an operators telephone set are established and broken in the use of the connecting circuits. Figs. (5. T, S and 9 show in detail the structure of one of the sequence switch mechanisms by which the circuits of the selector switch and other apparatus in the system are partly controlled. Figs. 6 and .7 are front and side elevations respectively, of the sequence switch, while Fig. 8 is a view in cross section on line 88 of Fig. 7, and Fig. 9 is a view in cross section on line 99 of Fig. 7.

Referring to shown in Fig.

the selector mechanism as l, the switch carriage or brush carrying member thereof is of the rotary type, the frame 2']. of which is mounted upon a central standard or shaft 22. At the outer end of the frame a number of sets of contact brushes 23,- 24, 25 are pivotally mounted upon but insulated from a rod 26, and from each other, over sets of line terminals 27,- 28, 29. The brushes have inwardly extending arms 30, bearin a ainst which, one for each i .1; one for each pivotally mo n upon a rod -nged normall tc acid the brush-s oeing rocked 0 line wi urinary terminals. .ring agai ends of the l: .cht are spring. i hold the latches fir against a 38. This stop rod 3 serves to prev en. :18 latches from being moved forward too far after the brushes have been released. A stop bar 35 serves to limit the outward movement of the brushes when the latches are withdrawn. The latches 32 and stop bar 35 are of insulating material so that the circuits connected with the brushes will not be crossed thereby. The springs 31 make electrical connection with the brushes; they are of sheet metal and form'the teeth of combs which connect corresponding brushes in the several sets in multiple. Suitable wire clip terminals 37. 3S and 39 are provided for the circuit connections to the springs and brushes.

As the brush carriage is rotated to cause swing in position to sweepthe brushes to sweep over the fixed terminals, the latches first pass by a tripping device or brush selector, by which any desired set of brushes may be released and caused to outwardly. This tripping device comprises a shaft 40 providedwith radially extending fingers 41 arranged spirally about the, surface of the shaft. This shaft is adapted by mechanism, to be presently described, to be rotated so as to bring the fingers one after anotherinto the line of travel of the several latches on the brush carriage. Only one set of brushes is intended to be released in a given operation.

The shaft isfirst rotated to bring a particular linger into position to engage the latch in the same level therewith and then the brush carriage is rotated. In passing, the outward edge of this latch strikes the end of the finger, allowing one set of three brushes to be released. Continued movement of the brush carriage brings the selected set of brushes into engagement with the rows of stationary terminals in the same level therewith, these brushes trailing over the terminals and making contact therewith in passin The brush carriage is finally caused'to stop with the selected brushes in contact with some one set of stationary terminals. The 'otherbrushes, not being released, are held out of contact with the terminals over which they pass. A further movement of the brush carriage in the same direction of rotation will carry the brushes over a restoring roller 69, which may be pivoted to the frame and which engages the free ends of the released set, causing them to be pushed back into their normal latched position. After making a full revolution, the brush carriage is brought to rest in its normal position again.

In the normal position of the brush carriage, as shown in Fig. l, a pair of levers 42, 43 engage at their'free ends a normal stop plate 46. At the end of lever 42 is' a roller 71 which lies .in a recess of plate 46, and at the end of lever 43 is a. right angle extension arm 72 which makes electrical contact with Said plate 46. 5 t. acting upon an inwardly extending arm it, serves to press the roller 71 with considerable force against plate 4?) and thereby holds the brush carriage securely in its normal position. A flat spring 52 engages an inwardly extending arm of the, lever 43.

roller 71 and the extension arm 72 engage.

the teeth of a cam plate The roller 71 A coil spring 7 into a notch.

rides over the teeth while the brushes are passing between terminals and drops into a notch as any released set of brushes is centrally located in direct contact with a set of terminals. The extension arm 72 follows behind the roller one tooth or notch and likewise engages a tooth as the brushes are passing between successive terminals. It. passes through the space between teeth,however, without touching the plate 50, as the released set of brushes is centrally located in contact with the terminals. The stop bar 35 engages the inwardly extending "arm 45 just as it does the arms 30 of the brushes and thus prevents the extension arm 72 of the lever 43 from touching the bottom of the notches between the teeth of plate 50, but permitting said arm 72 to touch. and make contact with the top of the teeth. The teeth and notches of plate are so spaced and arranged with res ect to the contact lever 43 that the extension arm 72 will not break contact with a tooth or plate 50 until after the brushes make contact with the stationary terminals and the roller 71 is ready to drop The circuit arrangement, as will presentl appear, such that the n otive power for driving the brush car e cannot be cut off until. the contact. thus broken between lever -13 and plae SO and therefore not until the brushes are in position to make good contact withthe stationary terminals. I

'The brush selector also provided with an interrupter or make and break contact device comprising an arm 56 pivoted to the frame at 57, engaging at its free end toothed wheel or cam 58 which rotates with the shaft 40. This arm 56 is adapted in the rotation of the shaft to engage two contacts 59 and 60. These contacts may be springs, the free ends only of which are shown in the drawin In its normal position the free end of the-arm 56 lies in a notch of the cam 58 which is deep enough to insure an open connection with contact 59. hen the shaft is away from its normal position, however, connection is made continuously with contact 59. The connection with contact 60- is intermittent, this Contact being made when the arm 56 is lifted by each tooth of the cam.

- There are as many teeth 'on the cam as there are fingers '41 on the shaft 40 and therefore as many as there are sets of brushes.

The motor mechanism for causing rotation of the brush carriage comprises an annular iron friction disk 61 flexibly mounted at the lower end of the shaft 22, an electromagnet 62 which may be fixed in any suitable manner'to the frame, and a constantly rotating shaft 63 carrying an iron drivingroller 64; The disk (31, roller 64 and that part of the shaft 63 which extends through the center of theelectromagnet 62 form the magnetic circuit of the electromagnet 62. When brushes shown.

I therefore current is passed through the winding of the magnet, the roller 64: attracts the disk 61 and causes the latter to rotate by frictional contact therewith. holding electromagnet 65 having a pole piece 66ex- 7 tending upwardly beneath the disk 61 is adapted when current is passed through its winding to enga e the-disk and hold it from movement. The power shaft 63 is extended as shown in the drawing to carry a flexibly mounted driving disk 70, which is adapted to engage a roller 67 carried by the spindle 40. An electromagnet 68 controls the engagement of disk Ti) and roiler 67 in the same manner that the electromagnet "62 controls the engagement of disk 61 and roller G-t. These devices'arc in fact electromag netic clutches, one to'cause movement of the brush carriage and the other to cause movement of the brush selector. The complete selector sw 'h mechanism is not shown in the draw/i ie ale ments thereof appear in their proper relation to one another so to make clear th manner in the mechanism operat Some of the circuits of the and connecting circuit trolled by a sequence swit h of the circuits of the its-tar Fig. 2, the cord finder of also of Fig. 3, and the t may be contr lled by general the function at t. is to establish in adefinite order sive stages of the operation the various ci cuits required to bring into service various devices or parts in proper sequence. The sequence switch consists in itseleme'nts of a 5 movable switch operating'member, a number of circuit changers actuated in sequence as said member is moved from one position to another, an electromagnet, and motor mechanism operated or-controlled by said magnet for advancing said movable member. In each position towhich a movable meme ber of the sequence switch is advanced, acirc'uit or set of circuits is established by which a given operation of the device under control- 'is made possible, and at the same time'an 5 other circuit is placed in a condition whereby the motor magnet of the sequence switch 'will first be closed for the motor advanced to the next position, until a new set of circu1ts is established, bringing about a new operation or electrical-condition of the device or devices under control, and so on.

adapted to be drawn into engagement with a friction roller 80 'by the action of a c utch magnebgl.

carried upon the shaft 76, The roller 89 and the d' 79 are 01 11011, and the'mctor magnet 8- adapted wheneis cited to inagnetize said roller 80, which serves as a rotary pole piece for said magnet; whereby the driving disk 79 is attracted into engagement with said roller, the rotation of the shaft 76 thus continuing as long as the motor magnet 81 remains excited.

The cams 77 carried by the rotary shaft- 70 are arranged to operate switch springs 82, forcing said springs into engagementwith outer contacts 83, or allowing them to engage their alternate inner contacts 84, according to the positions of said cams. As many cams and switches may be provided as the particular apparatus to be controlled may require. Certain of the switch contacts operated in the successive positions hf the movable switch element may control circuits for the motor magnet 81. A special switch, such as shown in Figz'il, is also preferably pro 'ided to control a local circuit for said motor magnet, whereby after the initial energizing circuit is broken by one or the other switches the motor magnet may still beer;- cited by current in the local circuit until the next intended stopping position of the rotary element is fully reached. As shown in Fig. 9, the cam 85 for operating the local switch is adapted to be engaged by a cam roller 86 carried by a pivoted switclhlever S7. A spring 88 is arranged to act upon said pivoted lever 8'? so as to press the cam roller 86 agaizmt the edge of the cam 85. When the roller 86 rides upon a tooth or high part of the cam 85, said lever 87 closes a contact sk i . 89 which controls the local circuit for the motor magnet. The teeth of the cam 85 have inclined edges, so that the cam roller 86, after riding over the point of a tooth, is forced down the opposite slope by the action of the spring 88, and this tends to push against the cam to continue the rotation thereof until the roller 86 reaches the bottom of the following notch. The rotary elements. is thus brought to rest accurately in or" the positions where it is intended to stop. In the operation of the device, the circuit magnet oughone of the springs 82 and one or sea the other of the contact anvils 83 or 8st of such spring. Then, as the motor magnet is excited and the shaft of the sequence switch begins to rotate, the contact through which the motor magnet was initially excited may be broken, but the local circuit will be maintained for the motor magnetthrough the contact 89 closed by the cam 85, and the rotary element will thus continue to advance until the cam roller 86 reaches the bottom of the next notch of the cam 85.

In Figs. 1 to 5, the switch springs of the sequence switches are not shown in their actual arrangement, but are so located as to 'give a clear arran ement of the circuits; and

the operatin cams are not shown. In Fig. 1, the clutch or motor magnet 81, its driving disk 79 and roller 80 are shown together with the various sequence switch springs and contacts 101 to 131 inclusive, the motor magnet, switch springs and contacts being located in the drawing in their proper circuit positions without particular regard to their structural arrangement as shown in Figs. 6 to 9. The positions of the rotary elements of each sequence switch in which any of its contacts (except contact 101) are closed, are indicated by numbers placed adjacent to such contacts; each contact being opened in all positions except those indicated by reference numbers. F or example, contact 103 is closed in the fourth, fifth, seventh, seventeenth and eighteenth positions as indicated by the numbers l, 5, 7, l7 and 1S, plac d adjacent thereto. In the case of the special contact 101 operated by cam .85, the numbers are placed on the opposite side of the switch lever from its contact anvil and indicate positions in which the contact is opened, such contact being closed continuously'while the rotary element of the sequence switch is in transit between the positions indicated. It will therefore be understood that the special contact 101 is closed continuously between positions 1 and 2, 2 and 3, 3 and 1, 4 and 6, 6 and 7, 7 and 8, 8 and 9, 9 and 10, 10 and 15, and 17 and 17 and l, but opened when the sequence switch is either resting in or passing by any one of these positions. There may he, say eighteen positions of the sequence switch, and the cams thereof will be caused to make one complete revolution in passing from normal (position 1) through the eighteen positions and back to normal again.

There are shown in Fig. 1 a number of other devices which enter into the control of the selector switch mechanism or are associated in some way with the cord circuit of which the selector forms a terminal. A plug 13% forms the other or answering terminal of the cord circuit. Connected in a local circuit leading to the sleeve of the plug is a cord relay 135, this relay controlling two back contacts 136 and 137 and two front includes two relays 165and 166, the former contacts 138 and 139. A superyisory lamp signal 140 is included in a local circuit controlled in part by a supervisory relay 141, the winding of which is included in a talking strand of the cord circuit leading to the answering plug 134.

A repeating coil 168 is interposed in the cord circuit between the plug 131 and the selector, windings 1 19 of this repeating coil being included with a battery 150 in that part of the circuit which leads to the plug, and windings 151 thereof being in cluded in that part of the circuit which leads to the selector. This latter part of the cord circuit maybe closed through contacts 119 and 120 of the sequence switch without including a source of current, or through contacts 118 and 121 with a battery 152. The battery 152 is shown in various parts of the circuit diagram merely to aid in tracing the circuits. A single battery is preferable, but if desired a number of batteries may be employed in different parts of the system. A line relay 153 is also included in that part of the cord circuit which leads to the selector, its winding, however, being shunted to voice currents by a condenser 154:. The line relay 153 controls a back contact 155 and a front contact 156, the front contact being connected to a ringing lamp signal 157 when.

the sequence switch is in the 9th position,

j and to a supervisory lamp signal 156 when the sequence switch is in the 10th position.

These lamp signals are arranged to indicate to the operator the condition of the switch hook at the called subscribers station.

For the purpose of controlling the restoration of the selector under certain conditions, a restoring or knock down relay 159 is arranged to be energized under the control of certain. switching devices to be manipulated by the operator. The circuit of this relay may be closed initially over a conductor including contact 116, closed when the sequence switch is in positions 2 to 6, and when so closed the relay becomes locked in a local circuit including contact 126 closed in positions 2 to 10 and front contact 160 of said relay. When energized this knockdown relay also opens a back contact 161 leading to various other sequence switch contacts and to the armature of line relay 153, and closes front contacts 162 and 163. Contact 162 is connected to sequenceswitch contact 109, the switch spring of which is in circuit with the motor-magnet 81 of the sequence switch. When this contact is closed, thes'equence switch iscaused to run by. a number of positions at which it would otherwise stop, and thus be immediately returned to normal. Contact 163 is connected through of the selector mechanism. 1

' The test circuit conductor for the selector having two windings, 167 of high resistance and 168 of low resistance, and the latter relay having but a single winding of low resistance. In the fourth position of the sequence switch, the test conductor is closed from test brush 25 through sequence switch contact 107, high resistance winding 167 of test relay 165, winding of relay 166, sequence switch contact 105 and back contact 161 of the knock-down relay 159, and as the brush carriage is moved to carry the brushesover the stationary terminals and the test brush resistance winding 167, thereby increasing the flow of current in the testcircuit and causing the energization of relay 166. This relay 166 will then open its back contact 170 and close its front contact 171. Contact 170 is connected to the motor magnet'62 of the selector brush carriage and contact 171 is connected to the motor magnet 81 of the sequence swltch and also to the holding magnet 65 of the brush carriage. The function of relay. 166 therefore is to control the movement of the brush carriage of the selector; and to cause it to stop at any-desired position. ..Test relay 165, by causing an increased flow of current in'the test circuit, will create a condition at the test terminal of. the line selected which will cause that line to test busy to other selectors. Leading from the conductor which joins relay 166 and the winding 167 of relay 165 is a branch conductor 172 which terminates in the spring 52. It will be remembered that this springmakes contact with lever 43, which in turn is caused to make ini i termittent contact with the teeth of -the'.

V grounded cam plate 50 as the brush carriage is'rotated. This branch connection therefore intermittently-shunts the winding of re lay 166, and the arrangement is such that the short-circuit is broken at periodic intervals which correspond to the positions in which it may be desired to cause the brush carriage to stop. That is to say, the shortcircuitv by way of conductor 172 is main tained while the brushes are traversing the spaces between successive stationaryv terminals and. is not broken until after the brushes have made good contact with saidtermihals.

Relay 165, however, is continuously in-cir cuit and responds the instant the test-brush 25 makes contact .w'iththe test; terminal 29- of an idle line. A moment later, when the brushes become centrally locatedin contact with the terminals, the short-circuitis interrupted and relay 166 responds, thereby opening the circuit of the motor magnet 62.

and closing the circuit of the holding magnet 65 in the manner before stated.

Referring to Fig. 2 which shows the operators listening set and switches associated therewith, it will be noted that the circuits are controlled by a sequence switch and a number of manually operable keys. The sequence switch is represented, in the same manner as the one in Fig. 1, by a motor magnet 281, a driving disk contacts 201 to 211 inclusive, contact 201 being the special contact corresponding in function to contact 101 of the sequence switch of Fig. 1. Contacts 209 and 212 are closed in all positions except the fifth and are interposed serially in the two strands of that part of the cord circuit which leads to the answering plug 131. In the fifth position, contacts 209 and 212 are opened and contacts 210 and 211 are closed. Contacts 213 and 211 are also'closed in the fifth po sition so that the cordeircuit is then completed by way of said contacts 210, 211, 213 and 211 and the normal contacts 228 of a ringing key 229. The contact spring for controlling sequence switch contacts 209 to 212 inclusive is of somewhat different construction from the other switch springs of the sequence switch. That is to say, these springs are so constructed that the opposing contacts are made and broken without interrupting the circuit. When the sequence switch is moving into the fifth position, contacts 210 and 211 will be made before contacts 209 and 212 are broken, and likewise .when the sequence switch is moving into the sixth positioncontacts 209 and 212 will be made before contacts 210 and 211 are broken. The ringing key 229 is adapted, when the sequence switch is in the fifth position, to ring back the calling subscriber by opening the cord circuit to the repeating coil windings 119 andconnecting a ringing generator 217 through the normally open contacts 230 in circuit with the calling line.

The operators telephone set may comprise a receiver 218, condenser 219, induction coil 220 and transmitter 221, the latter being in a local circuit with the primary winding of said induction coil 220 and a battery 222. The operators telephone set and the ring ing key 229 may be common to an operators position, while the ringing generator 217 may be common to the exchange or to one of the offices thereof. l In addition to the contacts controlled by the sequence switch, the operators keyboard equipment comprises an individual listening-in key 223, one for each cord circuit. a master listening-out key 221, a master wipeout key 225 and a master flash back key 226, the master keys being common to an operators position. The functions of these keys will be stated in the'description of the operation of the system. The sequence switch 279, a roller 280 and.

spring which controls opposing contacts 202 and 203 is connected by a conductor 227'to the corresponding springs of other listening keys of an operators position. Three such sequence switch springs are shown in Fig. 2.

A plurality of cord circuits and their listening switches are represented in Fig. 5 to show the manner in which the use of one may aifect the connections of another. In this figure there are also shown a plurality of subscribers lines, one of which is represented as extending from a substation 501 over line conductors 502 to a springjack 503 and to terminals 501 and 505 of automatic selector switches. The sleeve of the springjack is connected through a cut-off relay 506 to the free pole of battery .152. The line circuit is normally closed through a line relay 507 and contacts of said cut-off relay, this line relay controlling a line signal 508 in a local circuit; The arrangement is one which is commonly employed in telephone exchange systems.

In addition to the answering plug 131, cord relay 135, the listening key sequence switch clutch magnet 281, and contacts 201, 202, 203, 206 and 216 thereof which appear in Figs. 1 and 2, also there are shown in Fig. 5, answering plugs 231 and 2111 together with cord relays 235 and 215, magnets 286 and 291 and sequence switch contacts 211, 212, 213, 216, 256 and 261, 2 2, 263, 266 and 276. Two subscribers lines 512 and 522, other than line 502, with their springjacks 513 and 523 and cut-01f relays 516 and 526 are also indicated in Fig. 5. It may be assumed that any one of the three ar. swering plugs may be inserted by an'operator in any one of the spring jacks.

he circuits of the cord finder as shown in Fig. 3 are controlled by a. sequence switch comprising motor magnet 379, driving disk 381, roller 380 and contacts 301 to 308 inclu sive, while the circuits of the sender or controlling apparatus are governed by av sequence switch comprising motor magnet 391, driving disk 3S9, roller 390 and sequence switch contacts 351 and 361 inclusive.

The mechanism of the cord finder comprises five brushes 309 to 313 inclusive and as many sets of five stationary terminals 311 to 318 inclusive as there are cord connecting circuits in an operators position, eight sets being shown. a carriage adapted to rotate with a shaft 319, at the lower end of which is a flexibly mounted disk 320. This disk is adapted to be engaged by a roller 321 mounted on a continuously moving power shaft 322, the engagement being under the control of a motor magnet 323. The disk 320 is also adapted to be engaged by a holding magnet 321. The mode of control of the brush carriage by the magnets 323 and 321 is substan tially the same as that of the selector brush The brushes are mounted on carriage of Fig, 1, and a test relay 325 having a back contact 326 and a front contact 327 controls the circuits of said magnets in a manner similar to the control by relay 166 of motor magnet 62 and holding magnet 65 of the selector shown in Fig. 1.

The sender or controlling apparatus,

shown below and to the left of the cord finder in Fig. 3, comprises two series or strings of counting relays 331 to 338 inclusive and 341 to 348 inclusive, a stepping relay 362, a cut-off relay 363 and a relay 364.

for controlling the operation of the sequence switch. In addition to these relays, the circuit at the sender includes a reset relay 365.

: The function of the stepping relay 362 is to cause the successive operation of the counting relays. As will presently appear, this stepping relay is intermittently energized to alternately close its front contact 366 and its back contact 367. Relays 331 to 338 inclusive may be considered as the main co'unt- .ing relays, and relays 341 to 348 as-auxiliary thereto. Upon the first energization of stepping relayr362, a circuit is closed for the first auxiliary counting relay 341 from battery 152, sequence switch contact 359, winding of said relay 341, back contact 368 of the first main counting relay 331- and front contact 366 of said stepping relay 362.

{Belay 341 is thereupon energized and closes 331 thereupon closes its front contact 372 .which'isconnected to the first of a series of controlling switches or keys 391 to 398 in clusive. If this first key had been depressed,

'a circuit would then have been completed for relays 363 and 364 by way of sequence switch contact 353, said controlling switch I or key 391 and said front contact 372 of the I first named counting relay 331, whereupon the cut-off relay 363 would open at its back 610' .ner' described to operateand lock up the contact 373 the circuit of the stepping relay 362, while relay 364 would close a circuit for the motor magnet 391 of the sequence switch by way of the front contact 374 of said relay 364 and sequence switch contact ,357. It will be apparent that-'theinterinittent energization and deenergi'zatio'n' of the stepping relay 362 will continue in'the mancounting relays in succession until the front contact,- corresponding to contact 372 of some one of'the'mam counting relays closes closure will be determined in any case by the controlling switch or key which had been depressed. Thus if the eighth key 398 had been depressed, the stepping relay 362 would be energized eight times before the circuit for the cut-off relay 363 would be closed and the sending qfimpulses to the sending relay would be stopped.

A. reset relay 365 (Fig. 3) controls two front contacts 375 and 3.76 and a back con;

tact 377, contact 375 being adapted to closealocking circuit for said relay in shunt of se.--

quence switch contact 354, while contacts 376 and 377 are adapted to be connected to the motor magnet 391 of the sequence switch, contact 37 6 when the sequence switch is in normal position, and contact 377 when it is in all other positions, 2 to 18- inclusive.

301 and 351 are the special sequence switch contacts of Fig. 3 which correspond in function to contact 101 of the sequence switch of Fig. 1. A switch 378 is provided for the purpose of causing the sender sequence switch to'be moved out of the sec end position. This contact may be operated manually at the time a controlling switch or key is depressed to determine the operation of the selector of Fig. 1. It may, however, and in practice would be operated auto matically upon the closing of the controlling switch or key. It may be here stated that the complete arrangement of circuits and apparatus at the cord finder and sender for a large exchange system are notshown in Fig. 3; that is to say, only so much thereof is shown as enters into the control of the cord circuit, and selector mechanism ofFig. 1. In a large telephone exchange system, of which the system herein disclosed is a part, there would be several such selector mechanisms arranged to be operated in succession to establish a connection between subscribe-rs lines, and the sender mechanism would in such case comprise several sets of controlling switches or keys representing the several digits of the numbers assigned to the subscribers lines. In this application, however, the first or district switch only, and a single set of controlling switches or keys therefor are shown.

In Fig. 4 there are shown the circuits of a trunk line and a called subscribers line, together with the apparatus associated with said trunk line which enters in some respects into the control of the selector mechanism and signaling apparatus of Fig. 1. The

trunk line circuits are controlled in part by a sequence switch which is represented in this figure by a motor magnet 481, a driving disk 479, a roller 480 and contacts 401 to illf inclusive, contact 401 being the special contact corresponding in function to con- V I I V tact 101 of Fig. 1. The trunk line when ittogim t-Off relay 363 rand this extended to'a subscribers line may include 5 clertrmnagnet 413.

closed simultaneously with the selector concontacts of several successively operated selectors, the switch mechanism of which are not shown in the drawing. These are indicated, however, by contacts +111, 442 and There may be interposed in the trunk line a repeating coil 414., windings r15 of which are included in that part of the trunk circuit connected to the terminals of the selector of Fig. 1, and windings 4:16 of which are included, together with a battery 41?, in that part of the trunk line which is connected directly to a called line 118 leading to a substation T19. Included in that part of the trunk circuit which leads to the selector is a line relay 420, back contacts 421 and $22 of a battery control relay +23, and a battery 42%. \Vhen the battery control relay r23 is energized, that part of the trunk circuit which leads to the selector is closed at front contacts 425 and 426 but without including'the battery 124. The winding of line relay 420 is shunted to voice currents by a condenser 42?. This relay controls back and front contacts 428 and r29 res ectively,

while battery control relay 423 controls in addition to the contacts mentioned, back and front contacts T30 and 431. The arrangement of local circuits controlled by these contacts of relays 420 and 423 is such that 30 the sequence switch, after it leaves its nor the sequence switch. It will be noted that in the twelfth position of the sequence switch, the circuit of the called line includes a ringing generator +3-l and a winding L35 of a ringing control relay 436, this relay be ing adjusted to r spond to ringing current only when the subscriber takes his telephone from its hook in answer to the call. lVh-en so ener l, relay 43G closes a locking circuit by u ay ol front contact .237 and a set aid winding 38 of said relay, this ciracluding also the winding of superrelay 4:32. Upon entering the 17th posnion, the sequence switch closes contact -11 in circuit with a test.contact 412 and an Contact 412 would be tarts 4H2 and the energization of the electromagnet 413 would be the means of restoring the selector and thus causing the openj ot' the trunk line and local test circuits .id contacts H2 and 412. Similarly the rgization of an electroinagnet A4 in wire 175 would bethe means of restora selector controlling contacts all in the unit line.

Before describing the complete mode of operation of the system it may be stated with regard to the sequence switches that they are in each case advanced from position to position to control circuits for causing a particular operation of the mechanism associated therewith and that the several positions of the sequence switches are thus characterized and may be referred to either by the conditions which exist or by the operations which take place in those positions. Thus the positions of the selector sequence switch of Fig. 1 may be referred to as :Eol lows: 1, normal; 2, awaiting pressing of controlling key or switch; 3, transmitting impulses for selection; 4:, trunk hunting; 7, return on.knock-down connection; 9, ringing; 10, talking; 11 or 11, returning apparatus at'end of trunk line on disconnect; l5,

awaiting return of trunk line apparatus; 17,

return of switch.

In a similar way the positions of the listening key sequence switch are: 1, normal; 2, moving selector sequence switch. of? normal and moving another listening key from listening position; 5, listening, wipe out and flash back; 6, energizing knockdown relayonan incompleted pull down connection; 9,

off listening; 1, releasing selector apparatus on disconnect.

The cord finder sequence switch positions are: 1, normal; 2, hunting cord; 4, moving sender sequence switch off normal; 15, awaiting completion of selecting operations.

The sender sequence switch positions are: 1, normal; 2, awaiting pressing of controlling key or switch; 3, receiving impulses for selection; 18, awaiting completion of selecting operations.

releasing selector apparatus.

In the operation of the SJSliQin, a subscriber located at substatio 502 (Fig. 5) desiring conn other subscriber, located, s

n with anat subs ation t 119 Fi 4 may take his receiver 'rcm its 1 through the winding of cord relay 135,

sleeve of plug 134, sleeve of springjack 503, winding of cut-0d relay 506 to the free pole of said battery 152. -The cord relay and the cut-off relay are energized, the latter open-- ing the normal connections of the line circuit to the line relay 507 and. to ground, causing the extinguishment of the line signal 508.-

A circuit is now completed for the calling subscribers line from battery 150 (Fig. 1} through one half of Winding 14-9 of repeating The trunk line sequence switch positions are: 1, normal; 12, ringing; 13, talking; 17,

.front contact 138 of the cord relay 135.

spring of jack 503, tip contact of plug 134,:

conductor 181, listening key sequence swltch contact 209, conductor 190, the other half of winding 149 to the ground pole of said battery 150. Battery 150 thus supplies current to energize the transmitting telephone at the calling subscribers station.

The energization of the cord relay 135 which follows the insertion of the plug causes contacts 138 and 139 to be closed. Jontact 139 controls a local circuit for the answering supervisory lamp'signal 140, but

this lamp is not lighted at this time because the circuit is opened at the back contact 142 20 of the supervisory relay 141 which is energized by current in the circuit of the calling line. The closing of front contact 138, however, completes a circuit for the motor magnet 281 of the listening key sequence switch, this circuit including battery 152 (Fig. 2), the Winding of motor magnet 281, listening key sequence switch contact 216 and said The listening key sequence switch is thereupon caused to move from the first to the fifth or listening position. In passing positions -2 to 4 inclusive, a ground connection is made to the common conductor 227 which completes a circuit for any other llstenlng key sequence switch which may happen at that time to be in the fifth position. Such a cirouit may be traced in Fig. 5 as follows: From battery 152, the winding of the motor magnet of a listening key sequence switch in listening position, say motor magnet 291,

sequence switch contact 262 of said listening key, conductor 22? and sequence switch contact, say 203, of the listening key of the cord circuit being taken for use. The motor magnet 291 of the sequence switch in the fifth or listening position is now energized and causes the said sequence switch to move out of thesaid position into the ninth or offlistening position, whereit rests until the,

connection therethrough is taken down by the removal ofplug 244 from the springjack of the connected line. As the listening key sequence switch of the cord circuit now taken for use moves into the fifth position, contacts 210, 211, 213 and 214 are closed to connect the operators telephone set in abridge of the :cord circuit, while contacts 209 and 212 are opened. The cord circuit is now closed through the contacts mentioned and the nor mal contacts 228 ot the ring back key 229. The ClI'Cllt to the calling subscribers line is not interrupted even momentarily by this change in the cord circuit because of the continuity operation of the sequence switch 'rntacts 209, 210 and 211, 212.

As the listening key sequence switch (Fig. 2) moves out of normal position,'contact 215 is closed, thereby completing a circuit for the selector sequence switch as follows: Battery 152 (Fig. 1), motor magnet 81 of the selector sequence switch, contact 108 of said sequence switch, conductor l87,s aid contact 215 of the listening key sequence switch and the front contact 138 of cord relay 135 to ground. The selector sequence switch is thereupon caused to move into' the second position.

A number of contacts are closed by the selector sequence switch as it enters the second position as follows: Contact 109, which is connected to the listening key sequence switch contact 207; contact 116 which connects the winding of knock-down relay 159 to the master wipe-out key 225 through listeningkeysequence switch contact 204 now closed; contacts 121, 125 and 110 which connect line relay 153 in a loop circuit'leading through conductors 192 and 193 to stationary terminals 314 and 315 of the cord finder (Fig. 3); contacts106, 102.

and 104 which close connections from back I contact 161 of knock-down relay 159 to conductors 194, 196 and 197, respectively, lead-' ing to stationary terminals 316 and 318 and sequence switch contact 308. respectively of the cord finder; contact 131 which places a ground connection to conductor 183 leading to listening key sequence switch contact 205; contact 126 which places a ground connection to an armature of the knock-down relay 159; and contact 112 which connects the motor magnet 81 of the selector sequence switch to front contact 156 of line relay 153.

The closing of the selector sequence switch contact 104 completes a circuit for the motor magnet 379 or the cord finder sequence switch, whereupon said sequence switch moves from normal to the second position in which a circuit is closed for the cord finder motor magnet 323 by Way of sequence switch contact 304 and back contact 326 of test relay 325. The brush carriage of the cord finder is thereupon-caused to move .the brushes 309 to 313- over the rows of stationary terminals. W hen the brushes reach the terminals 314 to 318, which are connected to the cord circuit of Fig. 1, which is the one taken for use, a circuit will be completed for the test relay 325fby way of the cord finder sequence switch contact 302, conductor 386, brush 313, terminal 318, conductor 196, selector sequence switch contact 102 and back contact 161 of knock-down relay 159 to ground. The test relay thereupon opens at its back contact 326 the circuit of the cord finder motor magnet 323 and closes at its front contact327 a ,circuit for the holdin-g magnet 324, this latter circuit including sequence switch contact} 306, closed in two The cord finder is thus caused to stop with the'brushes 309 to 313 inclusive resting in contact with the terminals 314 to 318 inclusive, respectively, and conductors 192 to 196 inclusive are now extended to conductors 382 to 386 inclusive of the cord finder and sender. The closing of front contact of test relay also completes a circuit for the motor magnet 379 of the cord finder sequence switch, this circuit including sequence switch contact 307. Said sequence switch is thereupon moved from the second to the fifteenth position.

' Upon entering the fourth position, the cord finder sequence switchcloses a circuit for test relay as follows From battery 152 to winding of said test relay 325, cord finder sequence switch contact 303, conductor 38?, the winding of reset relay 365 associated with the sender, sender sequence switch con tact 351 .(now closed in normal position), conductor 38%, brush 311, terminal 316, conductor 19%, selector sequence switch contact 106 and back contact 161' of knock-down relay 159 to ground. Reset relay 365 is en ergized and it and test relay remain energized as the cord finder sequence switch moves to the fifteenth position. The back contact 326 of the test relay therefore is held open and said sequence switch comes to rest in the fifteenth position.

" The energization of the reset relay 365 causes the sender sequence switch to move from normal to its second position, a circuit being closed for the motor magnet 391 byway ofsender sequence switch contact 352 and front contact 376 of said reset relay 365. The circuit for the test relay 325 and reset relay 365 remains closed, when the sender sequence switch moves out of normal position, through a locking contact 375 of said reset relay.

The operations which occur as above stated upon the insertion of an answering plug into the springjack of a calling line, occupy .but a very brief interval of time. The cord finder may be constructed to move with great rapidity, the holding'magnet insuring that the brush carriage will stop at the terminals of the cord circuit which is taken for use. The selector sequence switch is now in the second position, the listening key sequence switch in the fifth position, the cord finder sequence switch in the fifteenth position'and the sender sequence switch in the second position. In the meantime the operator may inquire of the call ing subscriber" the connection that he desires, and upon learning the number of the line wanted, she may immediately depress controlling switches or keys corresponding to the digits of that number. 'Itis assumed in the system herein described that a single selector switch is to be operated under the control of the keys. The ,operator Will therefore depress but one key and it may be assumed that this is key 398. At the same time contact 378- may be closed to cause the sender sequence switch to move out of the second position into the third in which the sending operation takes place.

As the sender sequence switch moves into the third position, a circuit is completed including line relay 153 of the cord circuit (Fig. 1) and stepping relay 362 of the sender (Fig. 3) as follows: From battery 152 (Fig.1) through the selector sequence switch contact 121, the winding of said relay 153, selector sequence switch contact 125, conductor 192, cord finder terminal 314, brush 309, conductor 3S2, sender sequence switch contact 361, stepping relay 362, back contact 373 of cut-off relay 363, conductor v a' circuit for the selector sequenceswitch motor magnet 81 by way of the contact 112, the front contact 156 of said line relay 153 and the back contact 161 of knock-down relay 159. The selector sequence switch thereupon moves into the third position in which the brush selector is operated and in which impulses are transmitted over the sender circuit to the stepping relay 362.

The selector sequence switch upon reaching the third position, closes a circuit for the motor magnet 68 of the brush selector as follows: From battery 152 through the winding of said motor magnet 68, sequenceswltch contact 129, front contact 156' of line relay 153 and back contact 161 of the knock-down relay 159. The movement of the brush selector causes arm 56 to make intermittent connection with contact 60 and thus to intermittently short-circuit the stepping re lay 362 in the circuit previously traced for that relay and line relay 153. The line relay 153, however, remains energized until the sender circuit is finally opened by the operation of cut-off relay 363, which occurs when its circuit is completed through the depressed key 398, whereupon said line re lay is dei nergized, opening the circuit of the motor magnet 68 of the brush selector and closing at its back contact 155 a circuit for the motor magnet 81 of the selector sequence switch byway of switch ,contact 113. The brush selector is thus caused to stop with one of its fingers 41 pointing in the direction of the brush carriage and in trol relay 166, said sequence switch contact line with the travel of the latch 32. "At the same time theselector sequence switch moves out of the third position into the fourth, in which the brush carriage is ad-.

' lays which had been operated in succession and locked in local circuits, are released by the opening of sequence switch contacts 359 and 360. Also the circuit of the stepping relay 362 is held open by the opening of the contact 361, after the sender sequence switch leavesthe third position.

J Referring again to Fig. 1, it will be noted that the following contacts are closed in the fourth position of the selector sequence switch: Contacts 107 and 105 in the test cir- .cuit, and contact 103 in a conductor connected, to the armature of the motor control relay 166. The closing of said contact 103 completes a circuit for the motor magnet 62 of the brush carriage, which circuit includes back contact 170 of said motor con- 103 and back contact 161 of the knock-down relay 159. The brush carriage is thereupon caused to rotate and a set of three brushes 23, 24 and 25 are released from'the latch 32 as the brush carriage passes the brush selector and said latch strikes the finger 41. The movement of the brush carriage continues until the test brush 25 makescontact with a test terminal 29 of an idle line, whereupon test relay 165 is energized, closing its low resistance winding 168 in shunt of its high resistance winding 167, and cansing an increased flow of current in the test circuit, whereby said line will thereafter test busy to other selectors. A moment after the brush 25 touches terminal 29, a shortcircuit by way of .conductor l72, spring 52, arm 72 and ground plate 50, about the motor control relay 166, which exists while the brushes are passing between terminals is broken and said relay 166 is energized, open ing at its back contact 171 the circuit of the motor magnet 62 and closing at its front contact 171 a circuitjor the holding magnet 65. This last mentioned circuit may be traced from battery 152, through said holding magnet 65, said front contact 171 of relay 166, sequence switch contact 103 and back contact 161 of knock-down relay 159.

.The brush carriage is thus caused to stop with the brushes 23,.24 and 25 incontact with. terminals 27, 28 .and 29 of'an idle trunk line, comprising line conductors 173, 174 and test conductor 175. The line con-. ductors 173 and 174 may be extended as shown in Fig. 4 through contacts of other selector-mechanisms to a repeatingcoil 414 located at a distant or B ofiice. The energization of motor control relay 166 also caused the selector sequence switch to move out of the fourth position into the sixth, a circuit having been closed for the motor magnet 81 of said sequence switch by way of the front contact 171 of said relay 166, sequence switch contact 103 and back contact 161 of the knock-down relay 159.

The selector sequence switch may remain in the sixth position until the selector switch mechanisms other than the 'one shown in Fig. 1 have been successively operated under the control ofthe sender and have closed contacts 441, 442, 412 andv 443." According to the arrangement shown, however, in which there is but one selector, no time interval need be considered for such operations, and a circuit is closed for the motor magnet 81 of the selector sequence switch by wayof contact 112, conductor,195, cord finder terminal 317, brush 312, conductor 385, sender sequence switch contact 355, said sequence switch being at this time in the eighteenth position, conductor 384, brush 311 and terminal 316 of the cord finder, condnctor 194, selector sequence switch contact 106 and back contact'161 of knock-down relay 159. The selector sequence switch thus moves on to the seventh position in which a circuit for the motor magnet 81 is closed by way of the front contact 171 of relay 166, sequence switch contact 103 and back contact 161 of the knock-down relay. 159. The sequence switch therefore continues to the eighth position, whereina circuit is closed over the trunk line as follows: Battery 424 (Fig. 4) back contact 421 of the battery control relay 423, line relay 420, one half of winding 415 of repeating'coil 414, 0011- tarts 442 and 441 in the trunk line, conductor 173, terminal 27 of the selector, brush 23, conductor 176, one-half of winding 151 of repeating coil 148, selectorsequence switch contacts 119 and 120, line relay 153, the other half of winding151, conductor 177, brush 24, terminal 28, conductor 174, contacts-H1 and 442 in the trunk line, the other haltot winding 415' of repeating coil 414' and back contact 422 of battery control relay 423 to the ground pole of battery 424. Line relays 153 (Fig. 1) and 420 (Fig. 4) are energized in this circuit, the former 'closing a circuit for the motor magnet 81 of the selector sequence switch by Way of sequence switch contact 112, front contact 156 of said line relay 153 and back contact 161 of the knock-down relay 159. The se, lcctor sequence switch thereupon moves into the ninth. position, in which the trunk line circuit remains closed through contacts 119 and 120.

In the seventh position the selector sequence switch closes at contact 128a local circuit for the restoration of the brush selector.

As the selector sequence switch moves out of the sixth position, the cord finder test relay and the sender reset relay 365 are deenergized, the circuit heretofore traced including their windings being opened at contacts 112 and 106. The deiinergization ot' the test relay 325 causestlie cord finder sequence switch to move from the fifteenth position to normal, a circuit for its motor magnet 379 being closed by way of sequence switch contact 305 and back contact 326 of said test relay 325. The deenergization of the sender reset relay 365 causes the sender sequence switch to move from theeighteenth position to normal, a circuit for its motor magnet 891 being closed by way of sequence switch contact 353 and back contact 377 of said reset relay 365. The brush carriage of the cord finder remains in the position in which it had been placed to connect the sender-with the cord circuit, but it is otherwise restored to normal condition and is ready to associate the sender, which the first or normal position to the twelfth,-

which the ringing position: As the sequence switch enters the twelfth'position, a circuit is closed for the ringing generator 434 by way of sequence switch contact 406, contact 443, over he line circuit to substation 41! and there hrough the condenser and signal bell, returning by way of the other side of the line, contact 443, sequence switch contact 408 and winding 435 of the ringing control relay 430. The signal bell is sounded by current from the ringing generator over this circuit, and the ringing control relay adiusted to be irresponsive to such current The contacts 443 in the circuit to the called station may be the contacts of a. final selector switch, the mechanism of such switch and of other similar su itchcs in the trunk line circuit not being shown in the system herein described.

Upon thc response of the subscriber to circuit is closed from battery 417 by way of one-half of winding 416 of repeating coil 414, supervisory relay 432, winding 438 and front contact 437 of said relay 436 and sequence switch contiict 410 to ground. The armature of relay 436 is prevented from vibrating by reason of its winding 438 being included in this circuit. The supervisory relay 432 is now energized and a air cuit is closed for the motor magnet 481 of the trunk line sequence switch by way of sequence switch contact 404 and front contact 433 and of said supervisory relay 43 The trunk line sequence switch is thereupon caused to move from the twelfth into the thirteenth position in which the ringing eir cuit is opened at sequence switch contacts 406 and 40S and the circuit to the called subscribers station is closed at sequence switch contacts 407 and 409. A circuit is also closed in the thirteenth position from battery 424 through the winding of relay 423, sequence switch contact 405 and contact 433 of supervisory relay 432, where- .upon said relay 423 switches the battery 424 out of circuit of the trunk line by open ing its back contacts 421 and 422 and closes the trunk line circuit again without battery through its front contacts 425 and 426, The removal of battery 424 from the trunk line circuit causes the immediate deenergization of trunk line relay 420 which then opens its front contact 429 and closes its back contact 428. As the battery control relay 423 and the trunk line relay 420' are thus affected at the same or almost the same instant, the

motor magnet- 481 is not energizedand the trunk line sequence switch remains in the thirteenth position. The switching of battery 424 out of the trunk line circuit, however, causes the dei nergization of line relay 153 (Fig. 1) at the distant or cord circuit end of thetrunk line, whereupon a circuit is closed for the selector sequence switch which is now in the ninth position from batteiyl52 through motor magnet 81, sequence switch contact 113, back contact 155 of said line relay 153 and back contact 161 of lrnoclcdown relay 159 to ground, whereupon the selector sequence switch moves from the ninth to the tenth or talking position. The ringing lamp signal 157 is extinguished and is prevented from thereafter being lighted by the opening'of se quence switch contact 114, while the supervisory lamp signal 158 is immediately placed in position for subsequent operation, when the line relay 153 shall become energized, by the closing of sequence switch contact 115. The trunk line remains closed at sequence switch contacts 119 and 120 and the apparatus is now in position for telephonic communication from the calling station 501 to the called station 419.

At the termination of the period of con- 

